Impulse voltage generators are used to test high-voltage components, such as power transformers.
An impulse voltage generator can be used to produce a voltage impulse which is supplied by electrical means, to a part of a unit under test (UUT) to be tested, such as a high voltage winding, for example. The voltage impulse has a time duration that is normally in a range up to several tens of microseconds, and, depending on the UUT, the maximum voltage is up to several MV. Determinations regarding the state of the tested component, for example an age or presence of a fault in the electrical insulation, can be derived from continuous measurement of current and/or voltage values within the electrical circuitry of the test layout under the influence of the voltage impulse.
An impulse voltage generator can have a plurality of capacitors, which are charged and connected in parallel. The charged capacitors can be discharged and connected electrically in series to produce a high-voltage impulse. Thus, higher voltages can be achieved through the series connection of the capacitors. The impulse voltage generator has a structure which can be similar to a tower and include a capacitor, a resistor, a spark gap, and insulators, that are combined in a grid structure. The insulators can be in the form of tubes composed of an insulating material, for example glass fiber reinforced plastic (GFRP). The insulators can be arranged one behind the other along a length of the structure, to form a plurality of supporting columns that extend over the entire length of the tower structure. The operation of impulse voltage generators can be limited to a vertical, upright state, as this is the manner in which isolation separations can be maintained from any adjacent ground potential. The highest voltage occurs at the tip of the impulse voltage generator.
High-voltage components such as power transformers can be very heavy, and on the order of several hundred tons, depending on the electrical rating. Transporting a transformer of this size, when installed in an electrical power distribution system to a fixed installed test panel where the transformer can be subjected to an impulse voltage test in the course of servicing or diagnostic testing can be difficult given the high transport cost for the respective transformer. Furthermore, rarely does a power distribution system have sufficient redundancy to allow a transformer to be removed without adversely affecting system operation.
Impulse voltage tests such as those performed on power transformers can be carried out in without transporting the power transformer. The test arrangement that includes the impulse voltage generator and further components such as voltage dividers, and measurement and evaluation apparatuses, can be transported in a plurality of assemblies to the site where the transformer to be tested or to be serviced is located. There, the components and are assembled to form a test arrangement. The voltage divider, which can measure high voltages up to 2 MV, for example, can be a component of considerable size, such as a height of 10 m for example.
On-site assembly of the above-described test arrangement involves a considerable amount of time, in that the positioning and assembly of an impulse voltage generator or of a voltage divider are highly time-consuming.